The Leaning Tower of Pisa ( Italian: Torre pendente di Pisa ) or simply the Tower
of Pisa ( La Torre di Pisa ) is the campanile, or freestanding bell tower, of the
cathedral of the Italian city of Pisa. It is situated behind the Cathedral and is
the third oldest structure in Pisa's Cathedral Square ( Piazza del Duomo ) after
the Cathedral and the Baptistery.

Although intended to stand vertically, the tower began leaning to the southeast soon
after the onset of construction in 1173 due to a poorly laid foundation and loose
substrate that has allowed the foundation to shift direction. The tower currently
leans to the southwest.

The height of the tower is 55.86 m (183.27 ft) from the ground on the lowest side
and 56.70 m (186.02 ft) on the highest side. The width of the walls at the base is
4.09 m (13.42 ft) and at the top 2.48 m (8.14 ft). Its weight is estimated at 14,500
metric tons (16,000 short tons). The tower has 296 or 294 steps; the seventh floor
has two fewer steps on the north-facing staircase.

Before restoration work performed between 1990 and 2001, the tower leaned at an angle
of 5.5 degrees, but the tower now leans about 3.99 degrees. This means that the top
of the tower is 3.9 metres (12 ft 10 in) from where it would stand if the tower were
perfectly vertical.